The present invention relates generally to polyphase alternating current (AC) motors which have a main winding connectable to a voltage network and an auxiliary winding with the same phase number arranged in the stator. More particularly, the present invention relates to such an AC motor in which at least one condenser per phase is connected to the main and auxiliary windings and in which the conductors of the main and auxiliary windings are connected in series to increase the voltage applied to the condensers.
A polyphase AC motor is disclosed in U.S. Pat. No. 1,715,866. In this motor, the main and auxiliary windings are arranged so that the condenser voltage is in phase with the line voltage. As a result, it is possible to achieve the highest condenser voltage under otherwise identical conditions, thus achieving the smallest capacitance for the condensers. Similarly, the smallest no-load winding losses result. Since motors are normally operated only rarely at no-load, while they are, on the contrary operated predominantly under partial load conditions, it is a worthy goal if possible, for the minimum loss to occur within the range of partial load.
U.S. Pat. No. 4,187,457 discloses a motor in which in each phase, a condenser is wired in series with the main winding. As a result of the condensers, the average current density in the core of the stator is kept relatively high. Thus, high incoming currents are prevented from leading to currents in the motor that are too high. In addition, the condensers represent a form of overload protection. As a result of the auxiliary windings and the condensers, the operating characteristics should be improved, i.e., the way the motor behaves at start-up, the output factor, and the efficiency factor.
The present invention is directed to the problem of further developing a polyphase AC motor with main and auxiliary windings, one condenser per phase connected to the main and auxiliary windings, and in which the conductors of the main and auxiliary windings are connected in series to increase the voltage applied to the condensers, while also reducing losses in the range of the motor's load.